1. Field of the Invention
This invention relates to a sensor for an automobile, and more particularly to a sensor for an automobile of a type having a connection portion between a sensor body and a lead wire, the connection portion being covered with a coating material.
2. Description of the Related Art
FIG. 4 is a cross sectional view which illustrates a conventional crank angle sensor for an automobile. A crank angle sensor 1 comprises a sensor body 10, lead wires 20 for establishing the connection between the sensor body 10 and an external unit, and a connection portion between the sensor body 10 and the lead wires 20.
Initially, the sensor body 10 will now be described. Referring to FIG. 4, a body 11 is manufactured by molding resin. An L-shaped first guide 12 made of a magnetic material is attached to an end of the body 11. A magnet 13 is attached to the first guide 12. An L-shaped second guide 14 is attached to the body 11 in such a manner that the second guide 14 faces the first guide 12. Furthermore, a hole IC 15 is attached to the body 11 in such a manner that the hole IC 15 faces the magnet 13. For example, three insert terminals 16 serving as lead portions are embedded in the body 11 by insert molding. End portions of the insert terminals 16 are electrically connected to the hole IC 15, while other end portions of the same are formed into an external connection portion 16a outwardly projecting over the body 11.
Note that the second guide 14 and so forth are covered with a cover 17. A detection space 18 is formed between the first guide 12 and the magnet 13 and between the second guide 14 and the hole IC 15.
The lead wires 20 and the connection portion between the sensor body 10 and the lead wires will now be described. Referring to FIG. 4, each of the lead wires 20 has a core wire portion 20a, the outer surface of which is covered with a coating portion 20b. A rubber case 21 serving as the covering portion is opened in the upper portion thereof and at a portion thereof adjacent to the body 11, the rubber case 21 covering the lower portion of the external connection portion 16a of each of the insert terminals 16. The rubber case 21 is filled with a thermosetting filler 22 serving as a coating material so as to cover the upper portion of the external connection portion 16a of each of the insert terminals 16.
In the foregoing case, each of the lead wires 20 is inserted into the rubber case 21 through an end thereafor. The core wire portion 20a appearing in the leading portion of the lead wire 20 is caulked by a caulking portion 16b formed at an end of the external connection portion 16a of each of the insert terminals 16 so that the core wire portion 20a is held and then connected by soldering.
Then, the operation of the crank angle sensor 1 will now be described with reference to FIG. 5. A disc-like vane 2 made of a magnetic material is attached to an end of a crank shaft (not shown). The vane 2 has three projections 2a formed at, for example, the same pitch on the outer surface thereof. As shown in FIG. 4, the projections 2a of the vane 2, while rotating, move in the detection space 18 in the crank angle sensor 1 when the crank shaft is rotated.
In a case where the projections 2a of the vane 2 are not present in the detection space 18, a magnetic flux emitted from the magnet 13 forms a magnetic circuit passing through the first guide 12, the second guide 14 and the hole IC 15 and then returning to the magnet 13. In the foregoing case, the hole IC 15 detects the magnetic flux and transmits an ON signal. If the projections 2a of the vane 2 are present in the detection space 18, the magnetic flux emitted from the magnet 13 forms a magnetic circuit passing through the first guide 12 and the projections 2a of the vane 2 and then returning to the magnet 13. Since the magnetic flux of the magnet 13 does not reach the hole IC 15 in the foregoing case, the hole IC 15 does not detect the magnetic flux and transmits an OFF signal. Therefore, the crank angle sensor 1 detects the rotational angle of the crank shaft depending upon whether or not the hole IC 15 detects the magnetic flux.
The crank angle sensor 1 is disposed in the engine portion of an automobile in which corrosive gas and/or corrosive liquid is present and which is vibrated violently. Therefore, in the connection portion between the sensor body 10 and the lead wire 20, the connection between the insert terminals 16 and the lead wire 20 and the like must be satisfactorily sealed against gas and/or liquid, and disconnection of the lead wire 20 occurring due to vibrations must be prevented.
Therefore, the end of the rubber case 21 is attached to the body 11 of the sensor body 10 in such a manner that it elastically and hermetically comes in contact with the body 11. Thus, no gap is formed between the rubber case 21 and the body 11. The thermosetting filler 22 to be enclosed in the rubber case 21 is made of a material exhibiting sufficient bonding characteristics with respect to the rubber case 21 so that no gap is formed between the rubber case 21 and the thermosetting filler 22. Since the end of the lead wire 20 is supported by the rubber case 21 that can easily elastically be deformed, no stress concentration takes place in the area at which the lead wire 20 is inserted into the rubber case 21, or the like. Therefore, no disconnection takes place in the lead wire 20.
However, the foregoing crank angle sensor 1 must have a large number of elements in the connection portion between the sensor body 10 and the lead wire 20 thereof. Therefore, there arises a problem in that an excessively large number of manufacturing processes are required and accordingly the manufacturing cost cannot be reduced. What is worse, a long time is required to mount the rubber case 21 on the body 11, thus causing the cost to be raised. In a case where the thermosetting filler 22 in the rubber case 21 is hardened by injecting the foregoing elements in a hot bath set to a predetermined temperature level, the liquid thermosetting filler 22 flows over the rubber case 21. As a result, there arises a problem of an unsatisfactory manufacturing yield.